Embodiments of the present invention relate to equalizer circuitry.
In some transmission links (e.g., high speed transmission links), the input data (e.g., differential input data) is degraded due to frequency dependent losses. The frequency dependent losses include skin effect losses and dielectric losses of the transmission media. If not rectified, these losses can lead to intersymbol interference (ISI), which results in an increased bit error rate (BER). Equalizer circuitry (including equalizer stages) in the receiver is used to compensate for these losses so that subsequent stages (e.g., a sense amplifier in the slicer stage) can correctly detect the signal polarity.
One type of equalizer circuitry is a non-inductor based equalizer circuitry. A non-inductor based equalizer circuitry includes a plurality of non-inductor based equalizer stages. This type of equalizer circuitry is generally used in lower data rate applications (e.g., applications up to 14 Giga bits per second (Gbps)). It is to be noted that, in half rate architectures, the equalizer circuitry provides an alternating current (AC) gain at half the data rate. Thus, a non-inductor based equalizer circuitry is generally used to provide equalizer AC gains of up to 7 Giga Hertz (GHz). The non-inductor based equalizer circuitry, however, cannot achieve higher bandwidths because the capacitive loading on the output node starts limiting the bandwidth.
Another type of equalizer circuitry is an inductor based equalizer circuitry. An inductor based equalizer circuitry includes a plurality of inductor based equalizer stages. An inductor based equalizer circuitry achieves AC gain peaking at a higher bandwidth (e.g., for data rates greater than 20 Gbps). In the inductor based equalizer circuitry, the passive inductors help tune out the capacitive loading on the output node and increase the bandwidth of the AC gain. As inductors are not easily tunable, the bandwidth of an inductor based equalizer cannot be reduced to support lower data rates. Furthermore, inductor based equalizer circuitry have a larger footprint in layout.